The new 3.0 engine in the si model is incredible. Massive amounts of smooth power, beautiful sound when pushed hard, and a hard to believe 25+ mpg when driven hard. What truly makes the Z4 3.0si great is how well everything works together. The 6-speed manual tranny is perfectly matched to the engines power curve, the brakes have a perfect feel and no fade, the handling with the sport package is race car like.
Engine, styling, tranny, ohh did I mention the engine?
Tone down the active steering assist a little bit.